The present invention relates to an isotopomer absorption spectral analyzing apparatus and method for precisely assaying an isotopomerxe2x80x94a molecule containing an isotopexe2x80x94for inferring the origin thereof, contemplating applications in scientific fields, including environmental analysis; applications in the medical field, including diagnosis; and applications in other fields.
Conventional absorption spectral analyzing apparatuses employ a sample cell having a single optical path.
Therefore, when the isotope abundance ratio (the abundance ratio between two isotopes) deviates greatly from 1:1, a great difference is present between the levels of absorption signals corresponding to the isotope species, depending on the species of the isotopes. For example, in the case of naturally occurring CH4, the abundance ratio of 12CH4 to 13CH4 is approximately 100:1, and therefore, the absorption signal level of 12CH4 is approximately 100 times that of 13CH4, making precise measurement of the isotope ratio difficult.
The present invention has been accomplished so as to solve the aforementioned problem. Thus, an object of the present invention is to provide an isotopomer absorption spectral analyzing apparatus and method which enable absorption signals corresponding to different isotopes to assume substantially the same level, to thereby enable precise measurement of the isotope ratio.
In order to achieve the above objects, the present invention provides the following.
[1] An isotopomer absorption spectral analyzing apparatus, characterized in that a sample cell having a single window for introduction of at least two optical beams into the cell and being capable of providing optical paths of different optical lengths is installed; at least two optical beams are caused to enter the sample cell such that the optical beams travel along optical paths of different optical path lengths; and the abundance ratio between species of isotopes in molecules is determined from the ratio between intensities of absorption signals corresponding to the species of isotopes.
[2] An isotopomer absorption spectral analyzing apparatus as described in [1], wherein the at least two optical beams are emitted from a single light source of variable-wavelength type or from a plurality of light sources of fixed-wavelength type or variable-wavelength type.
[3] An isotopomer absorption spectral analyzing apparatus as described in [1], wherein the sample cell is a multiple-reflection absorption cell having paired reflection mirrors.
[4] A method of isotopomer absorption spectral analysis, characterized in that a sample cell having a single window for introduction of at least two optical beams into the cell and being capable of providing optical paths of different optical lengths is used in order to substantially equalize levels of absorption signals corresponding to species of isotopes, to thereby enable precise measurement of the abundance ratio between the species of isotopes.